Sharking Tagging Mission to Clipperton Atoll

By Michel Labrecque.

I remember watching, many years ago, a Cousteau episode about Clipperton Atoll that contained images of impressive schools of scalloped hammerheads cruising over virgin reefs. A little over a year ago, I happened on this episode again and was once more amazed by the quantity of sharks I saw. I started to wonder if things had changed around the atoll.

Given the massive decrease in shark populations worldwide, what would be the status of these apex predators around an isolated and uninhabited atoll? As a shark advocate I was curious to see for myself and so the idea of organising an expedition to Clipperton was born.

Remote and Uninhabited

Clipperton is located in a zone known as the ETP (Eastern Tropical Pacific). It lies 1,400km off the west coast of Mexico, on the same latitude as northern Costa Rica. San José del Cabo, on the tip of Baja California Peninsula, will be the departure point of our expedition. A crossing of 117 hours allows us to reach our destination.

Clipperton Rock is the most famous of landmark of the island.

Aside from its location, which has earned it the title of most isolated atoll on the planet, Clipperton’s history is surprising and complex. Disputed by many countries since the 1800s, it was finally declared a French Territory in 1931. The island has been uninhabited since 1945 and visited only sporadically by groups of scientists and the occasional illegal visitor.

A special authorisation, delivered by the French Government, is required to set foot on the island or to enter the territorial waters around the atoll, a 22km radius. Such authorisations are rarely granted and almost exclusively delivered to scientific missions given the uniqueness of the atoll.

I teamed up with an esteemed group of shark scientists: Dr Eric Clua from France, Dr Mauricio Hoyos Padilla from Mexico and Sandra Bessudo from Columbia. They oversaw and participated in our citizen/science diving expedition. The primary goal of this mission: to assess the health of Clipperton’s shark population and attempt to establish connectivity between other shark sanctuaries in the ETP such as the Cocos, Galapagos, Coiba, Malpelo Islands and the Revillagigedo Archipelago. The mission could also reveal residency of sharks around the island.

Isolated and Vulnerable

Seen from above, Clipperton is the picture-perfect image of an island paradise. The distance that separates it from the continent has, however, not protected it from man’s eagerness for profit. Clipperton is known as a tuna stronghold and commercial fisherman have been aggressively fishing the area for several decades. For political considerations, France signed an agreement with Mexico in 2007. Under this agreement, commercial fishing licenses are granted within the 200 nautical mile (370km) zone around the atoll. The licenses exclude the right to fish within the territorial waters.

We surprised an illegal tuna boat inside territorial waters. It is not clear whether they were after tuna or sharks.

During my short stay around the atoll, I observed a Mexican fishing vessel, clearly within the forbidden zone. In fact, the vessels’ chase boats were seen less than 50 metres from shore. Some crew members even set foot on the atoll!

On land, I found numerous traces of high-tech fishing in the area such as fish aggregation devices (FADs) with GPS and phone capabilities that are used to locate the schools of tunas. There were also countless nets, lines and buoys, as many on land as underwater. While diving, we saw very little signs of pelagic fish.

The Shark Tagging Mission

The most commonly encountered shark around the atoll is the silvertip. Juveniles were present in good numbers but adults were almost non-existent.

Clipperton’s shark populations should logically be in good health if not under pressure. I was fearing otherwise though, given the atoll’s remoteness and the prices shark fins are fetching. Underwater observations became our most valuable tool to better assess the population and the number of species. As suspected, a few short minutes after submerging, I saw overwhelming evidence of long-lining over Clipperton’s reefs. On every dive, several discarded lines were documented.

Satellite tags are attached to the dorsal fin and are programmed to detach and float after a period of six months. They will then transmit the data to a satellite for retrieval by the scientists.

The team carefully scanned the reef, on the lookout for sharks. We paid equal attention to potential sightings in blue water. On each dive, I saw many juvenile silvertip sharks (Carcharhinus albimarginatus) that were somewhat inquisitive – but only a few adults. According to scientists, the area is a nursery for this species. On very few occasions, I spotted adult Galapagos sharks (Carcharhinus galapagensis). Scalloped hammerhead sharks (Sphyrna lewini) were spotted twice off in the distance. I did not see the walls of sharks I was hoping to find.

Aboard the vessel, the citizens helped scientists to install acoustic and satellite tags on selected individuals. The tags will allow them to establish residency of sharks around the atoll as well as migration patterns of adult sharks. In doing so, they hope to prove connectivity, add Clipperton to the list of protected islands and eventually establish a migratory corridor for sharks.

The batteries of the receivers need to be changed after a certain period. The are also retrieved to download the data they contain.

During a previous mission, three acoustic receivers had been installed around Clipperton. The receivers are part of a network of over 150 receivers deployed in the ETP by members of MigraMar (of which Mauricio and Sandra are researchers). As of now, a little over 1,050 sharks have been tagged throughout the ETP, eight of which were tagged in Clipperton (three silvertip sharks, four Galapagos sharks and one silky shark).

As for the findings, connectivity between Cocos, Galapagos and Coiba has been clearly established and new evidence is now linking them to the Revillagigedo. The data collected during our expedition will be further analysed, but a summary overlook has revealed that sharks tagged around Clipperton are coming back to its waters. There is also clear evidence of silky sharks moving between the Galapagos Islands and Clipperton Atoll.

Moving Forward

Our 2016 mission to attempt to prove spatial connectivity for migratory shark species is already yielding results that favour the establishment of a Marine Protected Area (MPA) around Clipperton. French authorities are conscious of the threats the isolated atoll faces and have demonstrated clear interest in controlling access to the island and its surrounding waters. We are confident that the participation of French scientist Eric Clua will contribute to the advancement of the creation of protective measures. While it is difficult to create an MPA, enforcement of such a protected area is even harder.

Experience of other islands that have been granted the status of MPA shows us that without permanent presence on the island or in the waters surrounding Clipperton, illegal fishing is likely to continue. This stands to remain true as long as demand justifies fishing in such a remote location of the world.